I always carry a notebook with me for making sketches, or jotting down ideas. I have several different ones, as I often misplace one for a while, then have to take another. This one is only about 3.5" x 4.5" and I've had it for several years, so that sometimes the ink from previous entries bleeds through to the sketch or notes on the other side, as happened here.

Riding the subway on the way to or from work is a great way to see interesting faces. I saw this woman one day on the #6 train, when I was on my way to Whole Foods on 14th Street during my lunch hour.